﻿PLATE XII. 



UPPER SILURIAN CRUSTACEA. 



Order — Merostomata. 



Sub- Order — Eurypterida. 



Vterygotus bilobus, var. S, acidens. 



Fig. 



1 a. Represents an individual of the natural size. 



le. The larval eye-spots. 

 o, o. The compound eyes. 



a. One of the antennae. 



m. The metastoma, or post-oral plate. 



ec. One of the ectognaths. 



op. The operculum {c, its central portion). 



br. Some of the branchiae. 



The segments marked 15 and 16 are absent in the specimen. 



1 b. Antenna, magnified twice the natural size ; m, moveable ramus of chela. 



1 c. Some of the scale-like markings upon the surface of the thorax, greatly 



magnified. 



1 d. Some of the branchiae, enlarged twice the natural size. 



1 e. Thoracic plate restored (natural size). 



From the Uppermost Silurian of Lesmahago, Lanarkshire. 

 Drawn from a specimen in the Museum of Practical Geology, Jermyn Street. 



